Quorum is an open-source blockchain platform that is built upon Ethereum and focuses on data privacy and permissioned networks. It offers various consensus mechanisms to ensure the integrity and security of the network. This document will explore the different consensus mechanisms provided by Quorum, including QBFT, Istanbul BFT, Clique POA Consensus, and Raft-based Consensus.
QBFT (Quorum Beacon Fault Tolerance)
QBFT is a Byzantine fault-tolerant consensus mechanism designed for permissioned networks. It is based on the Tendermint consensus engine and is used in the Quorum Beacon Network. QBFT enables fast and secure consensus even when some nodes are compromised or unavailable.
Outcomes for QBFT
- Consensus: QBFT reaches consensus when a valid proposal is agreed upon by a supermajority of nodes (two-thirds of the network).
- Forking: Forking is prevented as QBFT requires a supermajority to agree on a single chain.
- Finality: QBFT provides finality, meaning that once a block is committed, it cannot be changed or reversed.
Source: Quorum Beacon Chain Specification
Istanbul BFT
Istanbul BFT is a Byzantine fault-tolerant consensus mechanism that allows Quorum to operate in a permissioned network with high throughput and low latency. It is based on the Tendermint consensus engine and is an alternative to the Ethereum consensus mechanism.
Outcomes for Istanbul BFT
- Consensus: Istanbul BFT reaches consensus when a valid proposal is agreed upon by a supermajority of nodes (two-thirds of the network).
- Forking: Forking is prevented as Istanbul BFT requires a supermajority to agree on a single chain.
- Finality: Istanbul BFT provides finality, meaning that once a block is committed, it cannot be changed or reversed.
Source: Quorum Specifications
Clique POA Consensus
Clique POA (Proof of Authority) Consensus is a consensus mechanism where transactions and blocks are validated by approved accounts, known as validators. It is used in Quorum’s private transactions and is an alternative to the Ethereum consensus mechanism.
Outcomes for Clique POA Consensus
- Consensus: Clique POA Consensus reaches consensus when a majority of validators agree on the validity of a block.
- Forking: Forking is possible but less likely as Clique POA Consensus relies on a smaller set of validators.
- Finality: Clique POA Consensus does not provide finality, meaning that blocks can be changed or reversed if a majority of validators agree.
Source: Quorum Specifications
Raft-based Consensus
Raft-based Consensus is a consensus mechanism designed for crash fault-tolerant systems. It is used in Quorum’s Raft-based ordering service, which provides a more robust and performant alternative to the Ethereum consensus mechanism.
Outcomes for Raft-based Consensus
- Consensus: Raft-based Consensus reaches consensus when a majority of nodes agree on the validity of a block.
- Forking: Forking is possible but less likely as Raft-based Consensus relies on a smaller set of nodes.
- Finality: Raft-based Consensus does not provide finality, meaning that blocks can be changed or reversed if a majority of nodes agree.
Source: Quorum Specifications
In conclusion, Quorum offers various consensus mechanisms tailored to the needs of permissioned networks. Each consensus mechanism has its unique properties and trade-offs, and understanding these outcomes is crucial for selecting the right consensus mechanism for a specific use case.
